Outer rotor brushless motor having an axial fan

ABSTRACT

A brushless direct-current motor is provided includes an inner stator and an outer rotor. The rotor includes a rotor core disposed around the stator, an inner annular member mounted on a rotor shaft, and a plurality of radial blades extending angularly from the rotor core to the inner annular member forming a fan. A first end cap is provided including a radial back plate proximate the fan and a center opening in the radial back plate through which the rotor shaft extends. A second end cap is provided including a main body disposed adjacent the stator opposite the fan. The radial back plate of the first end cap includes at least one sloped surface forming at least one air gap such that the airflow generated by the fan is centrifugally guided within the first end cap by the sloped surface and caused to exit through the air gap.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/837,935 filed Apr. 24, 2019 and U.S. Provisional Application No.62/881,105 filed Jul. 31, 2019, both of which are incorporated herein byreference in their entireties.

FIELD

This disclosure relates to an outer-rotor brushless motor, and moreparticularly to a high-power outer-rotor brushless motor for use inpower tools and outdoor products.

BACKGROUND

Conventional brushless direct-current (BLDC) motors are provided with apermanent magnet rotor supported within a stator. The stator includes aring-shaped stator core, a series of stator teeth that extend radiallyinwardly from the stator core, and a series of stator windings wound invarious patterns on the stator teeth. The rotor includes a rotor corethat supports a number of magnets and is mounted on a rotor shaft. Theshaft is supported relative to the stator via one or more bearings.

Another type of BLDC motor, referred to as an outer-rotor or externalrotor motor, is provided with the rotor on the outside of the stator. Inan outer-rotor motor, the rotor magnets are provided on an outer cupthat is rotatable around a stator core. The outer cup includes a plateon one side of the stator that is secured to a rotor shaft. US PatentPublication No. 2019/0058373, which is incorporated herein by referencein its entirety, provides an example of an outer-rotor motor in anailer, where the outer rotor includes an integrated flywheel fordriving a driver of the nailer. Outer-rotor motors provides someperformance advantages over comparable inner-rotor motors. Namely, sincean outer rotor is by necessity larger than an inner rotor, it createshigher inertia and reduces the torque ripple effect and lower vibration.An outer rotor also provides higher magnetic flux and is also capable ofproducing more torque than a comparable inner rotor motor.

Use of electric motors in battery-operated cordless outdoor productssuch as lawn mowers has gained popularity in recent years. Electricmotors, particularly brushless motors as described above, are capable ofproducing high amount of output power at a high degree of efficiencysuitable for such applications. Despite its advantages, use of electricbrushless motor in such products presents challenges relating toplacement and assembly of the motor in a compact and efficient manner.Moreover, as outdoor products are used in environments with high amountof debris, dust, and grass particulate, protection of the motor againstentry of debris and contamination is of great importance.

An impact tool such as a demolition tool or a hammer typically includesa tool holder in which a cutting tool can be supported and driven by animpact mechanism. The impact tool typically includes an electric motorthat converts electrical energy to a rotary motion and an impactmechanism by which the rotary output of the electric motor is converterto a linear motion. The impact mechanism repetitively strikes the end ofa cutting tool to impart axial impacts onto the cutting tool. The U.S.Pat. No. 10,328,558, which is incorporated herein by reference in itsentirety, describes an example of such a hammer drill that can operatein a hammer mode to perform this operation. In an impact tool, the motoris typically housed within a motor housing below the transmissionmechanism in a direction perpendicular to the longitudinal axis of thetransmission mechanism. A handle is typically attached at one end to theend of the motor housing and at the other end to the transmissionhousing. A battery receptacle may be located below the handle adjacentthe motor housing.

Once again, while outer-rotor brushless electric motors are capable ofproducing high amount of output power at a high degree of efficiencysuitable for impact power tools, placement of the motor in a compact andefficient manner and without significantly increasing the overall lengthand/or diameter of the tool housing presents challenges.

SUMMARY

According to an aspect of this disclosure, a brushless direct-current(BLDC) motor is provided. The motor includes a stator having a statorcore, teeth extending radially outwardly from the stator core, andwindings wound around the stator teeth; a rotor shaft extending along acenter axis; and a rotor having a rotor core disposed around the stator.The rotor includes permanent magnets secured to the rotor core, an innerannular member mounted on the rotor shaft, and a plurality of radialblades extending angularly from the rotor core to the inner annularmember forming a fan adjacent the stator that generates an airflow withrotation of the rotor shaft. A first end cap is provided including aradial back plate proximate the fan and a center opening in the radialback plate through which the rotor shaft extends. A second end cap isprovided including a main body disposed adjacent the stator opposite thefan. The radial back plate of the first end cap includes at least onesloped surface forming at least one air gap such that the airflowgenerated by the fan is centrifugally guided within the first end cap bythe sloped surface and caused to exit the first end cap through the airgap.

In an embodiment, first end cap further includes an annular body formedat least partially around the fan and the radial back plate extends fromthe annular body. In an embodiment, the annular body includes at leastone exhaust port in fluid communication with the at least one air gapand through which the airflow is expelled from the first end cap in asubstantially radial direction.

In an embodiment, two sloped surfaces are provided on two sides of thecenter opening of the first end cap, and two air gaps are formed betweenrespective ends of the two sloped surfaces. The two air gaps extend fromthe annular body of the first end cap towards the center opening tointersect a centrifugal path of the airflow within the first end cap.

In an embodiment, the first end cap includes a side plate projectingoutwardly around the annular body and a lower surface arranged to bemounted on a housing of a tool.

In an embodiment, the center opening of the end cap supports a frontbearing of the rotor shaft.

In an embodiment, the second end cap includes an annular body extendingform the main body around at least a portion of the rotor core, theannular body of the second end cap coming into contact and being securedto the first end cap.

In an embodiment, the second end cap includes a first set of openingsfor passage of airflow and a second set of openings for passage of a setof motor terminals arranged to electrically couple to the statorwindings of the stator.

In an embodiment, a stator collar is mounted on the stator core and theterminals are mounted on the stator collar in a direction parallel tothe rotor shaft.

In an embodiment, the second end cap includes a center opening withinwhich a sensor board is secured. The sensor board accommodatespositional sensors facing the rotor shaft. A sense magnet is mounted onthe rotor shaft facing the positional sensors.

According to another aspect of this disclosure, a brushlessdirect-current (BLDC) motor is provided including: a stator having astator core, teeth extending radially outwardly from the stator core,and windings wound around the stator teeth; a rotor shaft extendingalong a center axis; and a rotor having a rotor core disposed around thestator, permanent magnets secured to the rotor core, and an innerannular member mounted on the rotor shaft. A first end cap is providedincluding a radial back plate disposed on a first side of the stator andhaving a front center opening through which the rotor shaft is supportedvia a front bearing. A second end cap is provided having an innerannular body, an outer annular body, and a main body extending on asecond side of the stator from the inner annular body to the outerannular body. The inner annular body extends axially inwardly and formsa rear center opening. The inner annular body includes a first portionthat extends at least partially into an opening of the stator core andsupports the rotor shaft via a rear bearing, and a second portionrearward of the first portion that received a rear end of the rotorshaft therein and houses a sensor board therein, where the sensor boardaccommodates positional sensors facing the end of the rotor shaft.

In an embodiment, the rotor includes radial blades extending angularlyfrom the rotor core to the inner annular member forming a fan adjacentthe stator that generates an airflow with rotation of the rotor shaft.

In an embodiment, the radial back plate of the first end cap includes atleast one sloped surface forming at least one air gap. The airflowgenerated by the fan is centrifugally guided within the first end cap bythe at least one sloped surface and caused to exit the first end capthrough the at least one air gap. The first end cap includes an annularouter body having at least one exhaust port in fluid communication withthe at least one air gap and through which the airflow is expelled fromthe first end cap in a substantially radial direction.

In an embodiment, the annular body of the second end cap extends formthe main body around at least a portion of the rotor core and comes intocontact with the first end cap to secure the second end cap to the firstend cap around the rotor.

In an embodiment, the second end cap includes a first set of openingsfor passage of airflow and a second set of openings for passage of a setof motor terminals arranged to electrically couple to the windings ofthe stator.

In an embodiment, a stator collar is mounted on the stator core and theterminals are mounted on the stator collar in a direction parallel tothe rotor shaft.

In an embodiment, the first portion of the inner annular body has alarger diameter at the first portion that at the second portion.

In an embodiment, a sense magnet is mounted on the rear end of the rotorshaft in close proximity to the sensor board.

In an embodiment, the inner annular body further includes a thirdportion disposed between the first portion and the second portion andhaving a diameter that is greater than that of the second portion butsmaller than that of the first portion. In an embodiment, the sensemagnet is located within the third portion of the inner annular body.

In an embodiment, the inner annular body further includes a radial rimformed at a rear end of the second portion and the sensor board issecured to the radial rim. In an embodiment, an impact absorbing memberor a spring is disposed between the sensor board and the radial rim.

In an embodiment, the second end cap is provided with one or moredeflection limiting members near meeting boundaries of the outer annularbody and the main body. The deflection limiting member(s) face the rotorcore to absorb an impact of the rotor core in an even of a pivotingmovement of the rotor shaft away from the center axis.

According to another aspect of this disclosure a brushlessdirect-current (BLDC) motor is provided including a stator having astator core, teeth extending radially outwardly from the stator core,and windings wound around the stator teeth; a rotor shaft extendingalong a center axis; and a rotor having a rotor core disposed around thestator, permanent magnets secured to the rotor core, and an innerannular member mounted on the rotor shaft. A first end cap including aradial back plate is disposed on a first side of the stator and having afront center opening through which the rotor shaft extends. A second endcap is provided having an inner annular body, an outer annular body, anda main body extending on a second side of the stator from the innerannular body to the outer annular body, where the second end capincludes openings for passage of motor terminals electrically coupled tothe windings. A stator collar is mounted on the stator core and theterminals are mounted on the stator collar in a direction parallel tothe rotor shaft.

In an embodiment, three terminals are provided equidistantly around thestator collar.

In an embodiment, each of the plurality of terminals includes a mainbody and two side guide portions together having a curved contour, thetwo side guide portions configured to be received within axial guidechannels of the stator collar.

In an embodiment, each of the plurality of terminals includes two tangportions on one end proximate the stator extending angularly from themain body for connection to a respective one of the windings.

In an embodiment, the stator further includes an end insulator mountedon an end of the stator core and the teeth to electrically insulate theteeth from the stator windings.

In an embodiment, the end insulator includes an annular inner mountingplatform on which the stator collar is mounted and an annular rimprojecting from the mounting platform and disposed around the statorcollar.

In an embodiment, the stator collar has approximately the same diameteras the stator core. In an embodiment, the stator collar is sized suchthat the motor terminals are disposed along a circumference that issmaller than a circumference formed by the windings.

According to an aspect of this disclosure, a lawn mower is providedincluding a main deck defining a lower cavity within which a cuttingblade is received, wheels supporting the main deck, and a brushlessdirect-current (BLDC) motor mounted on the main deck for driving thecutting blade. The motor may be configured according to any of theabove-described embodiments, with the rotor shaft driving the cuttingblade. In an embodiment, airflow generated by the motor fan is caused toexit the motor above the main deck so as to substantially separate themotor airflow from the lawn mower cavity. In an embodiment, the lawnmower further includes a motor housing disposed above the main deck tohouse the motor, and a battery cage disposed above the motor housing forreceiving a removeable battery pack therein.

According to another aspect of this disclosure, a power tool is providedincluding a housing, a battery receptacle formed on the housing forreceiving a power tool battery pack, a control module disposed withinthe housing to control supply of power from the battery pack, and abrushless direct-current (BLDC) motor mounted within or on the housing.The motor is configured according to any of the above-describedembodiments. In an embodiment, the first end cap of the motor isintegrally formed with the housing.

According to yet another aspect of this disclosure, a power tool isprovided including a housing; a tubular cylinder housed within thehousing defining a longitudinal axis; a piston reciprocatingly disposedwithin the tubular cylinder; a crank mechanism disposed within thehousing configured to convert a rotary motion to a reciprocating motionfor driving the piston; and a tool holder mounted on the housing forwardof the tubular cylinder. A battery receptacle is provided on the housingfor receiving a removable power tool battery pack, the battery packbeing provided on a first side of a plane intersecting the longitudinalaxis when received within the battery receptacle. A brushlessdirect-current (BLDC) motor is mounted on the housing on a second sideof the plane intersecting the longitudinal axis. The motor includes astator having a stator core, teeth extending radially outwardly from thestator core, and windings wound around the stator teeth; a rotor shaftextending along a center axis oriented perpendicularly to thelongitudinal axis; and a rotor having a rotor core disposed around thestator, permanent magnets secured to the rotor core, and an innerannular member mounted on the rotor shaft. A first end cap of the motoris mounted on the housing, the first end cap including a radial backplate disposed on a first side of the stator and having a front centeropening through which the rotor shaft is supported via a front bearing.A second end cap provided outside the housing, the second end capincluding a main body disposed adjacent the stator.

In an embodiment, the motor counterbalances a weight of the battery packsuch that a distance between the longitudinal axis and a center ofgravity of the power tool with the battery pack received within thebattery receptacle is less than or equal to approximately 20% of a fullheight of the power tool.

In an embodiment, a handle is mounted on the housing, the handle havinga first end disposed adjacent the motor and a second end forming thebattery receptacle. In an embodiment, at least a portion of the secondend cap intersects a longitudinal axis of the first end of the handle.

In an embodiment, the first end cap supports the rotor shaft via a frontbearing and the second end cap supports the rotor shaft via a secondbearing. In an embodiment, the second end cap includes an inner annularbody that projects into the stator core to support the second bearingwithin the stator core. In an embodiment, at least a portion of thefirst end cap intersects a longitudinal axis of an upper wall of thetubular cylinder.

In an embodiment, the crank mechanism includes a crank wheel mounted onan end of the rotor shaft adjacent the first bearing, a pivoting pinmounted on the crank wheel offset from the rotor shaft, and a piston armextending form the piston and coupled to the pivoting pin.

In an embodiment, the first end cap is formed integrally with thehousing.

In an embodiment, the rotor includes radial blades extending angularlyfrom the rotor core to the inner annular member forming a fan adjacentthe stator that generates an airflow with rotation of the rotor shaft.

In an embodiment, the radial back plate of the first end cap includes atleast one sloped surface forming at least one air gap, wherein theairflow generated by the fan is centrifugally guided within the firstend cap by the sloped surface and caused to exit the first end capthrough the air gap. The first end cap includes an annular outer bodyhaving at least one exhaust port in fluid communication with the air gapand through which the airflow is expelled from the first end cap in asubstantially radial direction such that the airflow is substantiallyprevented from entering into the housing of the power tool.

In an embodiment, the radial back plate of the first end cap includesair vents that allow the airflow generated by the fan to enter the mainhousing in a direction of the center axis.

Additional features and advantages of various embodiments will be setforth, in part, in the description that follows, and will, in part, beapparent from the description, or may be learned by the practice ofvarious embodiments. The objectives and other advantages of variousembodiments will be realized and attained by means of the elements andcombinations particularly pointed out in the description herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of this disclosure in any way.

FIG. 1 depicts a perspective view of an electric mower, according to anembodiment;

FIG. 2 depicts a side view of an electric mower with a translucent mainbody, according to an embodiment;

FIGS. 3A and 3B depict front and rear perspective views of anouter-rotor brushless motor, according to an embodiment;

FIGS. 4A and 4B depict front and rear exploded views showing the innercomponents of the outer-rotor brushless motor, including rotor andstator assemblies and first and second end caps, according to anembodiment;

FIG. 5 depicts a side cross-sectional view of the outer-rotor brushlessmotor, according to an embodiment;

FIGS. 6A-6F depict perspective views of the outer rotor assemblycomponents through the course of the manufacturing assembly, accordingto an embodiment;

FIGS. 7A and 7B depict front and rear perspective views of the secondend cap, according to an embodiment;

FIG. 7C depicts a partial cross-sectional view of the motor showing abearing pocket of the second end cap receiving a bearing and a sensorarrangement, according to an embodiment;

FIG. 8A depicts a perspective view of the second end cap includingdeflection limiting members, according to an embodiment;

FIG. 8B depicts a partial cross-sectional view of the motor including animpact absorbing member behind the positional sensor board within thebearing pocket, according to an embodiment;

FIG. 8C depicts a partial cross-sectional view of the motor including aspring member behind the positional sensor board within the bearingpocket, according to an embodiment;

FIG. 8D depicts a wave spring used as the spring member of FIG. 8C,according to an embodiment;

FIGS. 9A and 9B depict front and rear perspective views of the first endcap, according to an embodiment;

FIG. 10A depicts a top view of the first end cap, according to anembodiment;

FIG. 10B depicts a top horizontal cross-sectional view of the first endcap, according to an embodiment;

FIG. 11A depicts a side view of the first end cap, according to anembodiment;

FIG. 11B depicts a side vertical cross-sectional view of the first endcap, according to an embodiment;

FIGS. 12A and 12B depict perspective views of the stator assemblyincluding a stator core and a stator collar prior to and after assembly,according to an embodiment;

FIGS. 12A and 12B depict perspective views of the stator assembly and astator collar, according to an embodiment;

FIG. 13A depicts a perspective view of the stator assembly includingstator windings and the stator collar mounted on the stator core,according to an embodiment;

FIG. 13B depict a partial zoomed-in perspective view of the statorassembly including the stator collar, according to an embodiment;

FIGS. 14A and 14B depict side and top views of the stator assembly,according to an embodiment;

FIG. 15 depicts a perspective view of a cordless electric hammer havingan outer-rotor brushless motor, according to an embodiment;

FIG. 16 depicts a side cross-sectional view of the hammer;

FIG. 17 depicts a partial zoom-in cross-sectional view of the hammer;and

FIG. 18 depicts a partial exploded view of the motor 500 relative to themain housing 602.

Throughout this specification and figures like reference numbersidentify like elements.

DETAILED DESCRIPTION

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide an explanation of various embodiments of thepresent teachings.

FIG. 1 depicts a perspective view of an electric mower 10, according toan embodiment. FIG. 2 depicts a side view of an electric mower 10 with atranslucent main body 12, according to an embodiment. As shown in FIGS.1 and 2, the electric mower 10 includes a main body 12 having a maindeck 52 and a motor housing 50. The electric mower 10 further includesone or more blades 14 rotatably supported in a cavity 16 defined belowthe main deck 52, a pair of front wheels 18 supported by the main body12, a pair of rear wheels 20 supported by the main body 12, and a handle22 extending rearwardly from the main body 12. A grass collection bag 54is supported on a rear side of the main body 12 below the handle 22.

In an embodiment, an outer-rotor brushless DC (BLDC) motor 500 coupledto a rotor shaft 340 is mounted in the motor housing 50 of the main body12 above the main deck 52 for rotatably driving the one or more blades14. The motor 500 may be arranged to drive the blades 14 by a directdrive mechanism (i.e., connecting the blade 14 directly to the rotorshaft 340). Alternatively, motor 400 may drive the blades 14 via atransmission mechanism including transfer gears, a transfer belt, and/orother speed and/or torque reduction and transmission components.

The handle 22 is provided with a pair of side rods 24 extending fromeither side end of the rear part of the main body 12 on two sides of thegrass collection bag 54, and a cross rod 26 extending between the rearends of the side rods 24. The cross rod 26 of the handle 22 is providedwith a lever 28 for operating the BLDC motor 500.

In an embodiment, a battery cage 30 is disposed above the motor housing50 for receiving a removable tool battery pack 32 therein. In anembodiment, the battery pack 32 may be a sliding power tool type batterypack having a 60V, 80V, 100V, or 120V maximum voltage. U.S. Pat. No.8,573,324, which is hereby incorporated by reference in its entirety,provides an example of a sliding power tool battery pack that slidinglycouples to a power tool. The battery cage 30 includes an angular openingsized to receive the battery pack 32 therein at an angle of, forexample, 15 to 45 degrees relative to a plane of the main deck 52. In anembodiment, the battery pack 32 is positioned so as to intersect an axisof the rotor shaft 340.

In an embodiment, a power module 40 is disposed in the main body 12within or adjacent the motor housing 50. The power module 40 includes aseries of power switches configured as a three-phase inverter circuitfor regulating supply of power from the battery pack to the motor 500.In an embodiment, a controller (not shown) is also disposed within themain body, as a part of the power module 40 or separately thereof, forcontrolling the switching operation of the power switches. Controllercontrols the power switches based on the position of the lever 28 tocontrol the average voltage supplied from the battery pack to the motor500.

In an embodiment, the motor 500 is supported within the motor housing 50in a way that all components of the motor 500 are positioned above theplane of the main deck 52. Additionally, motor housing 50 is providedwith two oppositely arranged exhaust vents 56 disposed above the maindeck 52 arranged to expel air away from the motor 500 in a directionradial to the motor shaft 340 above the main deck 52.

The motor 500 features are described here in detail.

FIGS. 3A and 3B depict front and back perspective views of the BLDCmotor 500, according to an embodiment. In an embodiment, motor 500includes a first end cap 100, also referred to herein as a deck plate ora motor plate, and a second end cap 200, also referred to herein as amotor cup or stator mount. In an embodiment, the first end cap 100 issecured to the main deck 52 of the main body 12 by any method known toone skilled in the art. Similarly, the first end cap 100 and the secondend cap 200 are coupled to one another by any method known to oneskilled in the art. Such known methods include, but are not limited to,fasteners, adhesive, a tongue and groove assembly, friction-fitting,press-fitting, etc.

In an embodiment, the first end cap 100 includes a center opening 126through which the rotor shaft 340 extends outwardly and one or moreradial exhaust ports 124A and 124B arranged circumferentially onopposite sides of the first end cap 100. The second end cap 200similarly includes a center opening 210 through which one or morecontrol signal cables (not shown) are received, and a series of openings220 and 222 disposed at a distance around the center opening 210. In anembodiment, stator terminals 440 to the power module 40 pass through oneor more of the openings 220. These features will be described later indetail.

In an embodiment, inlet openings 222 are air inlets align with one ormore air inlets (not shown) of the motor housing 50 that receiveincoming cooling air from the outside environment. In an embodiment,radial exhaust ports 124A and 124B align with exhaust vents 56 of themotor housing 50 to allow expulsion of hot air away from the motor 500above the main deck 52 and in a radial direction parallel to the planeof the main deck 52. This arrangement substantially isolates airflow forcooling the motor 500 components from the cavity 16 below the main deck52. This reduces ingress of contaminated air including dust and grassinto the motor 500. This also ensures that the airflow generates by theblade 14 within the cavity 16 is unimpeded by the airflow for coolingthe motor 400.

FIGS. 4A and 4B depict front and back exploded views showing thecomponents of BLDC motor 500, according to an embodiment. FIG. 5 depictsa cross-sectional view of the outer-rotor brushless motor 500, accordingto an embodiment. As shown in these figures, in addition to the firstend cap 100 and the second end cap 200, the BLDC motor 500 includes arotor assembly 300, a stator assembly 400, and the rotor shaft 340. Inan embodiment, the first and second end caps 100 and 200 are secured toone another via fasteners 110 or other means to substantially containand encapsulate the rotor assembly 300 and stator assembly 400components. These features are described herein in detail.

In an embodiment, stator assembly 400 is provided as an inner statorincluding a stator lamination stack 410 having a ring-shaped stator core402 and a plurality of stator teeth radially projecting outwardly fromthe stator core with slots formed therebetween. Stator windings 420 arewound around the stator teeth defining the phases of the BLDC motor 500.In an embodiment, where the BLDC motor 500 is a three-phase motorincludes 12 stator windings 420, the stator will constitute three groupsof four stator windings 420 connected together on or around the statorcore. The stator windings 420 within each group of stator windings 420may be electrically coupled together in a series of a parallelconnection, and the three groups of windings may be electrically wiredtogether in a wye or a delta configuration. In an embodiment, statorassembly 400 can further include one or more end insulators covering endsurfaces of the stator lamination stack 410 to electrically insulate thestator windings 420 from the stator lamination stack 410.

In an embodiment, stator lamination stack 410 has a thickness ofapproximately 8-14 mm, preferably approximately 10-12 mm, and a diameterof approximately 100-130 mm, preferably approximately 110-115 mm. Thus,in an embodiment, the stator lamination stack has a diameter tothickness ratio of approximately 8-12, preferably approximately 9-11, inan example approximately 10. In an embodiment, this ratio optimizes themotor for high power/high torque applications such as a lawn mower. Inan exemplary embodiment, the motor 500 has a maximum output speed ofapproximately 3,000 rpm, but a maximum power output of at least 1,100watts, more preferably at least 1,200 watts, in an example approximately1300 watts, suitable for high power/high torque applications.

In an embodiment, stator assembly 400 is secured, axially and radially,to the second end cap 200. The second end cap 200 is thus also referredto in this disclose as a stator mount. In an embodiment, ring-shapedstator core 402 of the stator assembly 400 is mounted and secured to aninner annular portion of the second end cap 200, as discussed later indetail.

In an embodiment, rotor assembly 300 is provided as an outer rotorincluding an inner annular member 322 and an outer annular core 320.Inner annular member 322 includes an inner through-hole that is securelymounted over the rotor shaft 340 by press-fitting or other known means.Outer annular core 320 is provided with a larger diameter than thestator assembly 400 so as to circumferentially surround the statorassembly 400 with a small airgap therebetween. Outer annular core 320supports one or more permeant magnets (discussed below) thatmagnetically interact with the stator windings 420, causing rotation ofthe rotor assembly 300 around the stator assembly 400 when the statorwindings are sequentially energized. Extending substantially radially orangularly between the inner annular member 322 and the outer annularcore 320 are a series of radial blades 326 that form a fan arranged togenerate airflow for cooling the motor 500 components, particularly thestator windings 440, as the rotor assembly 300 rotates. In particular,radial blades 326 are contained on their outer periphery by the annularcore 320, thus forming an axial fan that directs air parallel to theaxis of the rotor shaft 340. As will be described later in detail, firstend cap 100 is provided with features to redirect the air generated bythe axial fan in a radial direction.

In an embodiment, rotation of the rotor assembly 300 causes rotation ofthe rotor shaft 340 around its center longitudinal axis. In anembodiment, rotor shaft 340 is axially secured to the first and secondend caps 100 and 200 via front and rear bearings 130 and 230,respectively. Front and rear bearing 130 and 230 provide axial andradial support for the rotor shaft 340, and subsequently for the entirerotor assembly 300, with respect to the first and second end caps 100and 200, and subsequently with respect to the stator assembly 400. Thisarrangement ensures that the rotor outer annular core 320 is securelypositioned around the stator assembly 400 with an airgap in between.

Referring now to FIGS. 6A-6E, and with continued reference to FIGS.4A-5, details of the outer rotor assembly 300 and its assembly processare described herein, according to an embodiment.

FIG. 6A depicts a partial perspective view of the rotor assembly 300including inner annular member 322, outer annular core 320, and radialblades 326. In an embodiment, between approximately four to sixteenradial blades 32, more preferably between six to fourteen radial blades,and even more preferably between eight to twelve radial blades, areprovided. Each radial blade 326 can extend from an exterior portion ofthe inner annular member 322 to an interior portion 324 of the outerannular core 320. Interior portion 324 of the outer annular core 320 mayinclude an inwardly-projecting rim having curved portions that mate withradial ends of the radial blades 326. The radial blades 326 can beplaced at angles relative to a plane defined by the outer annular core320 and the inner annular member 322. The angular arrangement of theradial blades 326 forms openings 328 between adjacent radial blades 326,through which airflow is generated and passed towards the first end cap100. The geometry of the radial blades 326 can be in an airfoil shape toimprove an overall efficiency of the moving air.

FIG. 6B depicts a perspective view of a laminated back iron ring 310,according to an embodiment. FIG. 6C depicts a perspective view of thelaminated back iron ring 310, with permanent magnets 314 mounted on aninner surface thereof. In an embodiment, laminated back iron ring 310 isa ring-shaped lamination stack made of steel or other conductivematerial mounted within the outer annular core 320 of the rotor assembly300 to support permanent magnets 314. The laminated back iron ring 310can include magnet pockets 312 for holding the permanent magnets 314. Inan embodiment, the number of the magnet pockets 312 can correspond tothe number of the permanent magnets 314. In an embodiment, there may bebetween four to sixteen permanent magnets 314, more preferably betweensix to twelve permanent magnets 314, and even more preferably betweeneight to ten permanent magnets 314. The number of permanent magnets 314is determined as number of poles and slots of the motor 500.

In an embodiment, each magnet pocket 312 can be formed into aperipherally elongated rectangular shape. In an example, each magnetpocket 312 may also be curved to match the curvature of the laminatedback iron ring 310. Each of the permanent magnets 314 inserted into thecorresponding magnet pocket 312 can be a sintered neodymium magnet,which is formed into a shape corresponding to the magnet pocket 312.Furthermore, the permanent magnets 314 are magnetized so that themagnets adjacent to each other have poles reverse to each other.

As shown in FIGS. 6A-6C, the inner surface of the outer circular member324 can include a design to receive the laminated back iron ring 310. Tothis end, in an embodiment, the inner surface of the outer circularmember 324 can include protrusions 332 that can correspond to grooves319 on the laminated back iron ring 310. The interior portion 324 of theouter annular core 320 provides a platform for mounting and placement ofthe lamination back iron ring 310.

In an embodiment, as shown in FIG. 6D, the laminated back iron ring 310and the permanent magnets 314 are at least partially encapsulated by anovermold layer 316 including resin or plastic material via an overmoldor insert-mold process. In an embodiment, the overmold layer 316substantially covers the permanent magnets 314 and forms molded-inairflow reliefs 318 between the respective magnets 314.

FIG. 6E depicts a perspective view of the outer rotor assembly 300including the overmolded laminated back iron ring 310 of FIG. 6D,according to an embodiment. In an embodiment, the laminated back ironring 310 having the permanent magnets 314 and being, at least, partiallyencapsulated by overmold layer 316 is slip-fitted to the outer annularcore 320. In an embodiment, the protrusions 332 of the outer annularcore 320 are aligned with the grooves 319 of the laminated back ironring 310 and the laminated back iron ring 310 is received into the outerannular core 320.

In an embodiment, the laminated back iron ring 310 is secured to theouter annular core 320 by any known methods, such as by an adhesive toform the rotor assembly 300. In an embodiment, the laminated back ironring 310 is first inserted into the outer annular core 320 and then thepermanent magnets 314 are secured into the magnet pockets 312 by anyknown methods, such as by an adhesive. The overmold layer 316 may thenbe applied to the laminated back iron ring 310 having the permanentmagnets 314 to form the rotor assembly 300.

FIG. 6F depicts a perspective view of the rotor assembly 300 mounted onthe rotor shaft 340, according to an embodiment. As previouslydiscussed, in an embodiment, inner through-hole 330 formed within theinner annular member 322 of the rotor assembly 300 is press-fitted onthe rotor shaft 340. The rotor shaft 340 is thus axially, radially, androtationally secured to the rotor assembly 300. As also previouslydiscussed, rotor shaft 340 is further secured, axially and radially butnot rotationally, to first end cap 100 and the second end cap 200 viafront and rear bearings 130 and 230, respectively.

This arrangement provides an outer-rotor assembly having permanentmagnets disposed around the outer circumference of a stator assembly,but also coupled to a central rotor shaft rotatably received within thestator assembly. This arrangement also integrates fan blades forming anaxial fan for cooling the motor into the outer rotor assembly structure,ridding the motor of a separate fan structure.

In an embodiment, the rotor laminated back iron ring 310 has a diameterof approximately 120-150 mm, preferably approximately 130-140 mm, in anexample approximately 136 mm. The entire rotor assembly 300 includingthe outer annular core 320 has a diameter of approximately 130-160 mm,preferably approximately 140-150 mm, in an example approximately 145 mm.In an embodiment, the rotor laminated back iron ring 310 hasapproximately the same thickness as the stator lamination stack 410.

Referring now to FIGS. 7A, 7B and 7C, and with continued reference toFIGS. 4A-5, the second end cap 200 is described herein in detail.

FIGS. 7A and 7B depict front and back perspective views of second endcap 200, according to an embodiment. FIG. 7C depicts a zoom-incross-sectional view of the second end cap 200.

In an embodiment, second end cap 200 includes an outer annular body 202,an inner annular body 206 forming the center opening 210, and a conicalor dome shaped main body 204 extending between the inner annular body206 and the outer annular body 202. In an embodiment, front peripheraledge 208 of the outer annular body 202 is disposed to mate with thefirst end cap 200, as discussed later.

In an embodiment, center opening 210 of the inner annular body 206 formsa pocket 240 facing the first end cap 200 that securely supports therear bearing 230 of the rotor shaft 340 therein to axially and radiallysupport the rotor shaft 340 with respect to the second end cap 200.Additionally, pocket 240 houses a sense magnet ring 250 including aseries of magnets is mounted on a distal end of the rotor shaft 340rearwardly of the rear bearing 230. Moreover, pocket 240 houses andsupports a positional sensor board 260 including a series of positionalsensors (e.g., Hall sensors) in close proximity to and facing the sensemagnet ring 250. The positional sensor board 260 is oriented on a planesubstantially parallel to the longitudinal axis of the rotor shaft 340.

In an embodiment, pocket 240 includes a bearing pocket 242 at an end ofthe pocket 240 closest to the second end cap 200. The bearing pocket 242(i.e., first portion of the inner annular body 206) has a first diametersized to form-fittingly receive the rear bearing 230 of the rotor shaft340 therein.

In an embodiment, the pocket 240 further includes a sense magnet pocket244 disposed rearward of the bearing pocket 242 with respect to thesecond end cap 200. The sense magnet pocket 244 (i.e., third portion ofthe inner annular body 206) has a second diameter smaller than the firstdiameter, sized to freely receive and house the sense magnet ring 250therein. In an embodiment, radial rim 246 formed between the bearingpocket 242 and the sense magnet pocket 244 forms as an axial stop forthe rear bearing 230.

In an embodiment, the pocket 240 further includes a positional sensorboard pocket 248 (i.e., second portion of the inner annular body 206)disposed rearward of the sense magnet pocket 244 with a third diametersmaller than the first and second diameters. In an embodiment,positional sensor board pocket 248 is sized to form-fittingly receivethe positional sensor board 260 therein, with magnetic (hall) sensors262 in close proximity to the sense magnet ring 250 at a distance of,for example, 0.5 to 3 mm, preferably 0.2-2 mm, and approximately 1 mm.The magnetic sensors 262 detect a magnetic field generated by the sensemagnet ring 250 magnets to detect a rotatory position of the rotor shaft340. In an embodiment, a radial rim 247 formed between the positionalsensor board pocket 248 and an inner wall 249 of center opening 210forms an axial stop for the positional sensor board 260. In anembodiment, positional sensor board 260 may be fastened to the radialrim 247 or the side walls of the positional sensor board pocket 248 via,for example, screws or other fastening means. Communication signals fromthe positional sensor board 260 may be passed through the center opening210 for communication with the controller (not shown).

In an embodiment, the bearing pocket 240 protrudes inwardly towards thestator assembly 400 from the second end cap 200, with at least thebearing pocket 242 protruding axially into the inner opening of thering-shaped stator core 402 of the stator assembly 400. This arrangementallows the rear bearing 230 to sit within the inner opening of thering-shaped stator core 402 in-line with the stator lamination stack 410along the same radial plane. Further, the sense magnet ring 250 isin-line with at least a portion of the stator windings 420 along thesame radial plane. The arrangement according to this embodiment reducesthe axial length of the BLDC motor 500 and flattens the overallenvelope.

In an embodiment, one or more openings 220 are disposed in the main body204 at a first radius around the center opening 210 through which thestator terminals 440 (i.e., for receiving U, V, W phase power lines fromthe power module 40) are received. In an embodiment, the statorterminals 440 project slightly out of the openings 220 to ease wrappingor fusing of power lines to the terminals 440. In an embodiment, airinlets 222 are disposed in the main body 204 along a second radiusgreater than the first radius around the center opening 210 forreceiving incoming cooling air into the second end cap 200 for airflowgenerated by the motor fan.

In an embodiment, as briefly discussed above, the inner annular portion206 of the second end cap 200 structurally, i.e., radially and axially,supports the stator assembly 400. In an embodiment, the ring-shapedstator core 402 is sized to be mounted around the inner annular portion206 of the second end cap 200, with the stator lamination stack 410being disposed circumferentially around the bearing pocket 242. Thisstructure ensures that the stator assembly 400 is securely pilotedwithin the second end cap 200 with high precision.

In power appliances such electric mower 10 utilizing the motor 500described herein, the rotor assembly 300 can be seen deflectingdrastically upon high impact resulting from contact between the mowerblades 14 and a hard object such as a rock or metal object, particularlyingress of such hard object within the blades 14. In some instances,rotor assembly 300 can be seen pivoting around an axis that isperpendicular to the general axis of the motor 500 to deflect upwardlyin the direction of the second end cap 200. In an embodiment, thedeviation of the rotor shaft 340 from the longitudinal axis of the motor500 causes the rotor assembly 300 to pivot around an axis perpendicularto the axis of the motor 500, one side of the rotor assembly 300 makingcontact with the stator assembly 400 and the second end cap 200. Anycontact between the rotor assembly 300 in its rotating state and thenon-rotating parts of the motor 500 including the stator assembly 400and the second end cap 200 can cause severe damage to the motor 500components.

To limit the deflection of the rotor assembly 300 in the event of suchcontact or ingress of hard objects with or into the mower blades 14,according to an embodiment of the invention, the second end cap 200 isprovided with one or more deflection limiting members 270, as shown inthe perspective view of FIG. 8A. In an embodiment, deflection limitingmembers 270 may be made of flexible and/or elastically resilientmaterial such as plastic, rubber, etc. In an embodiment, deflectionlimiting members 270 may be secured to an inner surface of the main body204 of the second end cap 200 bordering the outer annular body 202. Inan embodiment, deflection limiting members 270 may be provided as aseries of discrete segments provided at a distance from one another, asshown in FIG. 8A, or as a one-piece ring sized to be received within theouter annular body 202. In an embodiment, deflection limiting members270 may be provided as integral ribs projecting from the main body 204and/or the outer annular body 202 of the second end cap 200, or asseparate pieces assembled into the second end cap 200.

In an embodiment, deflection limiting members 270 are provided with aheight 272 (in the axis direction of the motor 500) that is smaller thanthe distance between the rotor assembly 300 and the main body 204 of thesecond end cap 200. In an embodiment, the height 272 of deflectionlimiting members 270 is sized so that the rotor assembly 300 does notcontact the deflection limiting members 270 during normal operation andwith a normal level of vibration and movement, but is prevented bydeflection limiting members 270 from pivoting drastically so as to comeinto contact with the stator assembly 400.

In an embodiment, a thickness 272 (in the radial direction of the motor500) of the deflection limiting members 270 is sized to come intocontact with the rotor assembly 300, i.e., peripheral end of thelaminated back iron ring 310 or the overmold layer 316, but not with thestator assembly 400. In an embodiment, deflection limiting members 270are disposed along a ring having a diameter that is greater than thediameter of the stator assembly 400 but approximately corresponds to thediameter of the laminated back iron ring 310 of the rotor assembly 300.

In the event of high impact resulting from contact or ingress of hardobjects described above, the upward deflection of the rotor assembly 300may also at times make contact with and damage the positional sensorboard 260. This is particularly due to the small air gap that ismaintained between the positional sensor board 260 and the sense magnetring 250 for accurate sensing of the angular position of the rotorassembly 300.

To absorb this impact and protect the positional sensor board 260 fromdamage, according to embodiment, an impact absorbing member 280 isprovided, as depicted in the partial cross-sectional view of FIG. 8B. Inan embodiment, impact absorbing member 280 is received within sensorboard pocket 248. Impact absorbing member 280 may be fastened to theradial rim 247 or the side walls of the positional sensor board pocket248 via, for example, adhesive, screws or other fastening mechanism. Inan embodiment, positional sensor board 260 is in turn secured to theimpact absorbing member 280 via, for example, an adhesive, screws, orother fastening mechanism. In an embodiment, impact absorbing member 280may be made of flexible or resiliently elastic material such as densefoam, rubber, etc. In an embodiment, impact absorbing member 280 may beprovided with the sufficient thickness to effectively absorb the forceof an impact upon the positional sensor board 260 by the rotor shaft 340and/or the sense magnet ring 250, while maintaining proper airgapbetween the sense magnet ring 250 and the positional sensor board 260.In an embodiment, impact absorbing member 280 may be 1-3 mm inthickness. In an embodiment, impact absorbing member 280 may bedisc-shaped or ring-shaped with an outer diameter that is substantiallyequivalent to or greater than the positional sensor board 260.

In an embodiment, the impact absorbing member may be a spring element282 provided to absorb the impact on the positional sensor board 260, asdepicted in the partial cross-sectional view of FIG. 8C. In anembodiment, spring member 282 may be a wave spring, though other typesof spring such as a Belleville washer, disc spring, compression spring,torsion spring, etc. may alternatively be utilized. In an embodiment,spring member 282 is sized to be received within the sensor board pocket248 and secured to the radial rim 247 or the side walls of thepositional sensor board pocket 248 via, for example, adhesive, screws orother fastening mechanism. In an embodiment, positional sensor board 260is in turn secured to the impact absorbing member 280 via, for example,an adhesive, screws, or other fastening mechanism. In an embodiment,spring member 282 may be provided with the sufficient thickness toeffectively absorb the force of an impact upon the positional sensorboard 260 by the rotor shaft 340 and/or the sense magnet ring 250, whilemaintaining proper airgap between the sense magnet ring 250 and thepositional sensor board 260. In an embodiment, spring member 280 mayhave a thickness of 1-3 mm.

FIG. 8D depicts a perspective view of a wave spring used as the springmember 282, according to an embodiment.

The first end cap 100 is described herein in detail with reference toFIGS. 9A-11B, and with continued reference to FIGS. 4A-5, according toan embodiment.

FIGS. 9A and 9B depict front and back perspective views of the first endcap 100, according to an embodiment. FIG. 10A respectively depict a topperspective view and a top horizontal cross-sectional view of the firstend cap 100 along the y-z plane, according to an embodiment. FIGS. 11Aand 11B respectively depict a side perspective view and a side verticalcross-sectional view of the first end cap 100, according to anembodiment.

In an embodiment, as previously discussed, rotor shaft 340 passesthrough central opening 126 of the first end cap 100 to protrude intothe main deck 52 of the electric mower 10 for driving the blades 14.Moreover, the central opening 126 includes a bearing pocket 128 sized toform-fittingly and securely receive the front bearing 130 of the rotorshaft 340. The front bearing 130 secures the rotor assembly 300 withrespect to the first end cap 100 axially and radially, while allowingfree rotation of the rotor assembly 300 within the first end cap 100.

Additionally, the first end cap 100 includes a radial back plate 120facing the rotor assembly 300, an annular body 118 formed around theradial back plate 120, and a donut-shaped side plate 116 projectingoutwardly around the annular body 118 along substantially the same plateas the radial back plate 120. A rear peripheral edge 117 of the annularbody 118 comes to contact with front peripheral edge 208 of the secondend cap 200 to substantially circumferentially enclose the rotor andstator assemblies 300 and 400.

In an embodiment, radial back plate 120 is disposed adjacent radialblades 326 that form the fan of the rotor assembly 300. The back plate120 acts as a baffle for the fan, redirecting airflow generated by thefan to be expelled out of the exhaust ports 124A and 124B in a directionradial to the rotor shaft 340. In an embodiment, back plate 120 includesat least one sloped surface, for example, two sloped surfaces 120A and120B, as shown in FIGS. 9B, 10B, and 11B. The two sloped surfaces 120Aand 120B of the back plate 120 are each sloped with respect to a radialplane of the back plate 120 such that adjacent ends of the two slopessurfaces 120A and 120B are axially offset with respect to one another,forming two air gaps 123A and 123B therebetween. Each of the air gaps123A and 123B extends from approximately the outer portion of thebearing pocket 128 to approximately an inner portion of the rearperipheral edge 117 of the annular body 118. The air gaps 123A and 123Bare formed parallel to the x-y plane in FIG. 9B, where the x axisdesignates the longitudinal axis of the motor shaft 340. The air gaps123A and 123B extend laterally into the annular body 118, forming airchannels that are in fluid communication with the radial exhaust ports124A and 124B. Radial exhaust ports 124A and 12B are formed over theside plate 116. As airflow generated by the fan comes into contact withthe back plate 120, the sloped surfaces 120A and 120B cause centrifugalcirculation of the airflow within the first end cap 100. Air gaps 123Aand 123B intercept the centrifugal circulation path of the airflowwithin the first end cap 100, causing the air to exit the first end cap100 in a radial and/or lateral direction through the exhaust ports 124Aand 124B. Arrangement of the exhaust ports 124A and 124B above the maindeck 52 of the electric mower 10 ensures that hot air existing the motor500 does not enter the cavity 16 of the mower 10. The two slopedsurfaces 120A and 120B of the back plate 120 can form baffles that canprovide a cyclonic path for the airflow generated by the radial blades326 to be directed towards the two radial exhaust ports 124A and 124B.

In an embodiment, each of the sloped surfaces 120A and 1208 is aninclined surface, which has a starting end adjacent to the radial blades326 of the rotor assembly 300 and a terminal end adjacent to the each ofthe corresponding exhaust ports 124A and 124B.

In an embodiment, each of the sloped surfaces 120A and 1208 extend fromthe starting end to the terminating end along the circumferentialdirection with a substantially constant width from the starting end tothe terminal end. Two connecting walls 122A and 1228 connect the outeredge of each of the sloped surfaces 120A and 1208 to the first end capbody. Each of the connecting walls 122A and 1228 can extend from thestarting end of its corresponding sloped surfaces 120A and 1208 and tothe terminating end of each of its corresponding sloped surfaces 120Aand 1208.

In an embodiment, main deck 52 includes a corresponding through-holethat aligns with the central opening 126 for receiving the rotor shaft340. In an embodiment, a series of screws are received through thecavity 16 of the main deck 52 through corresponding through-holes of themain deck 52 (not shown) and peripheral receptacles 125 of the first endcap 100. A series of slugs or threaded nuts 112 are provided on the sideplate 116 of the first end cap 100 to securely receive the screws andfasten the first end cap 100 on top of the main deck 52. For thisreason, the first end cap 100 is also referred to as the deck mount inthis disclosure.

In an embodiment, the overall motor assembly 500 includes an envelope ofapproximately 140-180 mm, preferably approximately 150-170 mm, in anexample approximately 160 mm, as defined by the diameter of the annularbody 118 of the first end cap 110 and the diameter of the second end cap200. Furthermore, the length of the more, as defined between the lowerend of the first end cap 100 and the upper end of the second end cap200, is approximately 60-100 mm, preferably approximately 70-90 mm, inan example approximately 80 mm. This approximately 2:1 ratio of themotor diameter to height provides for a high torque, high power,planar-shaped motor that can be flatly mounted on top of the main deck52 of the mower 10.

Aspects of the stator assembly 400 are described herein in detail withreference to FIGS. 12A-14B, and with continued reference to FIGS. 4A-5,according to an embodiment.

FIGS. 12A and 12B depict perspective views stator assembly 400 with astator collar 430 prior and after assembly onto the ring-shaped statorcore 402 of the stator assembly 400, according to an embodiment. FIG.13A depicts a perspective view of the stator assembly 400 including thestator windings 420, with the stator collar 430 mounted thereon,according to an embodiment. FIG. 13B depicts a perspective zoomed-inview of the stator assembly 400 showing a single stator terminal 440 ofthe stator collar 430, according to an embodiment. Additionally, FIGS.14A and 14B depict side and top views of the stator assembly 400,respectively, according to an embodiment.

In an embodiment, stator teeth 406 extend radially from the stator core402. Each of the stator teeth 406 is wound by a stator coil to form thestator windings 420. The stator coils can be separately wound on thestator teeth 406 or continuous wound on the stator teeth 406, in aseries or parallel and delta or wye configuration, as discussed above.In an embodiment, each of the stator teeth 406 is substantiallyT-shaped.

In order to electrically isolate the stator coils from the statorlamination stack 410, the end insulators 412 may be provided. In anembodiment, end insulators are discrete components mounted on the endsof the stator lamination stack 410, or at least partially encapsulatethe stator lamination stack 410 by a process, such as an over-moldprocess. The end insulators 412 can be made from a material such asplastic or resin.

In an embodiment, stator collar 430 can include asubstantially-cylindrical insulation carrier 432, which may be formedfrom plastic material. Additionally, the stator collar 430 can include aseries of stator terminals 440, such as three stator terminals 440,mounted on the insulation carrier 432 and electrically insulated fromeach other by the insulation carrier 432. In an embodiment, each of thestator terminals 440 can be pressed into the stator collar 430. In anembodiment, the stator collar 430 includes a series of side openingswith railings or channels 444 arranged parallel to the center axis ofthe stator collar 430 (and center axis of the motor 500) along the sideopenings. The stator terminals 440 include two side guides 446 that areslidingly received within the railings or channels 444 to affix thestator terminals 440 within the side openings of the stator collar 430.

In an embodiment, at least one of the end insulators 412 of the statorassembly 400 includes an inner annular rim 404 that supports mountingthe stator collar 430 on the stator assembly 300. The insulating carrier432 of the stator collar 430 is annular and can be fixed to or be placedinside or on the inner annular rim 404 of the end insulator 412. In anembodiment, end insulator 412 includes a central opening formed withinthe annular rim 404 with a larger diameter than central opening 411 ofthe stator lamination stack 410. This arrangement exposes a donut-shapedmounting platform 414 of the end surface of the stator lamination stack410 facing the stator collar 430. A lower portion 434 of the insulatingcarrier 432 includes an outer diameter that is smaller than the outerdiameter of the insulating carrier 432, sized to fit within the annularrim 404 and rest on top of the mounting platform 414 of the end surfaceof the stator lamination stack 410.

In an embodiment, end insulator 412 can also be provided with a seriesof tabs 416 projecting axially (in parallel to the longitudinal axis ofthe motor 500) from or adjacent to the annular rim 404. Stator collar430 similarly includes recessed surfaces 448 that removably receive thetabs 416 for positioning and retention of the stator collar 430 over theend insulator 412. In an embodiment, the tabs 416 or the recessedsurfaces 448 may include snaps 449 for improved retention of the statorcollar 430 over the end insulator 412.

In an embodiment, end insulator 412 further includes a series ofrecessed surfaces 417 that extend radially through the annular rim 404into the outer surface of the teeth of the end insulator 412. Statorcollar 430 is similarly provided with a series of radial protrusions 447that are removably received within the recessed surfaces 417. Therecessed surfaces 417 and radial protrusions 447 may be provided withsnaps or other known retention features for securing the stator collar430 over the end insulator 412.

In an embodiment, this configuration of the stator assembly 300 andstator collar 430 allows the stator collar 430 to be interchangeablewith another one that has different types and/or quantities of statorterminals. The stator collar 430 may include different solder points forthe terminals, different junctions for the terminals, different weldconnections for the terminals, or a different number of terminals (e.g.,for a 6-phase controlled motor v. a 3-phase controlled motor). Differentstator collars 430 may be chosen by a motor designer based on, forexample, the thickness of stator winding wires and/or the number ofturns of windings around each stator tooth, the series or parallelconnections between stator windings in the same phase, the delta or wyeconnections between stator windings of different phases, etc. Forexample, the dual-tang configuration described above may be more suitedfor a motor design with relatively thick stator windings.Interchangeability of the stator collar 430 allows a motor designer toadapt the same stator assembly 300 for different applications by only.

In an embodiment, stator collar 430 is provided with terminals 440 amain body 452 of which includes a curved contour when viewed in theaxial direction of the motor 500 to form a uniform profile on the statorcollar 430. In an embodiment, referring to FIG. 13B, each of the statorterminals 440 is a monolithic member, which includes at least two tangs442 integrally extending radially-outwardly from the main body 452 ofthe stator terminal 440. This arrangement allows multiple sets of statorwires to be wound on the same terminal, increasing the capacity of eachof the stator terminals 440. The two tangs 442 may be arranged at anangle from each other in the radial direction to simplify the fusing ofthe stator wires and aid in the winding of a coil. In this case, thestator terminals 440 may be arcuately shaped.

An alternative application of the outer-rotor BLDC motor 500 isdescribed herein with reference to FIGS. 15-17, according to anembodiment.

FIG. 15 depicts a perspective view of a cordless electric hammer 600,according to an embodiment. FIG. 16 depicts a side cross-sectional viewof the hammer 600.

Referring to these figures, hammer 600 comprises a main housing 602. Inan embodiment, a handle 604 having two ends is attached to the mainhousing 602 via an upper mounting assembly 606 havingvibration-absorbing features and a lower mounting assembly 608 having apivoting member that allows slight pivoting of the handle 604 relativeto the main housing 602. U.S. Pat. No. 10,137,562 titled “Rear Handle,”which is incorporated herein by reference in its entirety, describes anexample of the rear handle 604 and its mounting assemblies.

In an embodiment, a battery receptacle 610 is provided below the handle604 rear of the lower mounting assembly 608. The battery receptacle 610is configured to removably receive and lock in a power tool battery pack612. Battery pack 612 may be, for example, a power tool 60V MAX batterypack configured to be slidingly received and secured within the batteryreceptacle 610. In an embodiment, the battery receptacle 610 includes aseries of battery terminals 614 supported by the lower end of the handle604 that engage and receive power from corresponding terminals of thebattery pack 612.

In an embodiment, a control module 616 is further provided within thehandle 604 for controlling the operation of the hammer 600. A triggerswitch 618 may be supported by the handle 604 for engagement by a userforward of the control module 616. Control module 616 controls flow ofpower from the battery pack 612 based on an input from the triggerswitch 618.

In an embodiment, hammer 600 further includes a cylindrical housing 620disposed forward of the main housing 602. A tool holder 622 is providedforward of the cylindrical housing 620 for holding tools such as achisel (not shown). Cylindrical housing 620 houses a tubular cylinder624 and includes a pneumatic hammer mechanism for driving the chisel ina reciprocating motion. The pneumatic hammer mechanism includes a piston626 located within tubular cylinder 624 and arranged for reciprocatingmotion, a ram 628 also arranged within the tubular cylinder 624 forwardof the piston 626 for reciprocating motion, an air chamber 630 locatedwithin the tubular cylinder 624 between the piston 626 and the ram 628to transfer reciprocating motion of the piston 626 to the ram 628, and abeat piece 632 located forward of the ram 628 for transferring thereciprocating motion of the ram 628 to a striking force on the chisel.Details related to the hammer mechanism and its components can be foundin, for example, U.S. Pat. No. 9,925,653 titled “Hammer Drill,” and U.S.Pat. No. 7,331,407 titled “Vibration Reduction Apparatus for Power Tooland Power Tool Incorporating Such Apparatus,” both of which areincorporated herein by reference in their entireties.

In an embodiment, a brushless outer-rotor motor 500, as described abovewith reference to FIGS. 3A through 14B, is mounted on the main housing602 of the hammer 600. In an embodiment, first end cap 100 of the motor500 is mounted on the main housing 602 such that the motor 500components are positioned substantially outside an extension envelopedefined by the cylindrical housing 620. In an embodiment, motor 500 isfully positioned above a horizontal plane formed by longitudinal axis‘A’ of the hammer 500, whereas battery receptacle 610 is fullypositioned below the same plane. In an embodiment, a portion of thefirst end cap 100 intersects a longitudinal axis ‘13’ of the upper wallof cylindrical housing 620 and/or an upper wall of the tubular cylinder624. In an embodiment, a portion of the second end cap 200 intersects alongitudinal axis ‘C’ of the upper mounting assembly 606 of the rearhandle 616. In an embodiment, the upper end of the main body 602 nearthe upper mounting assembly 606 is secured to the second end cap 200 foradded structural support of the motor 500 relative to the hammer 600.

FIG. 17 depicts a partial zoom-in view of the hammer 600. FIG. 18depicts a partial exploded view of the motor 500 relative to the mainhousing 602. As shown here, and with continued reference to FIGS. 15 and16, in an embodiment, motor 500 includes the same stator 400, rotor 300,first end cap 100, and second end cap 200 as described above, with firstend cap 100 shaped to be suitably mounted on top of the main housing 602or disposed within a cavity provided on the main housing 602.

In an embodiment, rotor shaft 340 extends perpendicularly to thelongitudinal axis ‘A’ of the hammer 600 from the motor 500 and throughthe main housing 602. Rotor shaft 340 is supported relative to thestator assembly 400 via rear bearing 230, as described above in detail.In an embodiment, rear bearing 230 is fully located outside the mainhousing 602 as well as the extension envelope defined by the cylindricalhousing 620. Rotor shaft 340 is further supported relative to the firstend cap 100 via front bearing 130. In an embodiment, front bearing 130intersects the longitudinal axis ‘B’ of the upper wall of cylindricalhousing 620 and/or an upper wall of the tubular cylinder 624.

In an embodiment, a lower end of the rotor shaft 340 is coupled to acrank wheel 642 within the main housing 602. The crank wheel 642 iscaused to rotate about the axis of the rotor shaft 340 by rotation ofthe rotor shaft 340. In an embodiment, a piston arm 644 extendsrearwardly from the piston 626 and penetrates into the main housing 602.The crank wheel 642 is coupled to end of the piston arm 644 via apivoting pin 646. Rotary motion of the crank wheel 642 is transferred toa reciprocating motion of the piston arm 644 via the pivoting pin 646.

In an embodiment, crank wheel 642 may mounted on the rotor shaft 340 by,for example, press-fitting or alternative mounting means. Directmounting of the crank wheel 642 on the rotor shaft 340 provides for adirect-drive mechanism without any reduction gears, which reduces heatloss and increases efficiency. Electronic commutation of the motor 500by control unit 616 allows for optimization of motor speed and poweroutput as required without a need for gear reduction system. In anembodiment, motor 500 may be controlled to output a maximum power of1300 W to 1700 W, preferably approximately 1500 W, at a rotational speedof 2000 to 3000 RPM, suitable for direct drive of the hammer 600.Alternatively, the crank wheel 642 may include gears that mesh withcorresponding gears on the rotor shaft 340.

In an embodiment, 60V Max battery packs having capacity rating of 3 Ahto 12 Ah may be utilized to power the hammer 600. These battery packsmay have a weight range of 2.5 to 4.5 lbs. One advantage of dispositionof the motor 500 above the main housing 602 and opposite the batteryreceptable 610, as described above, is more efficient balancing of thehammer 600. In an embodiment, the above-described configuration ensuresthat the hammer 600, when provided with a 60V Max battery pack, has acenter of gravity that is significantly close to the centrallongitudinal axis ‘A’ of the hammer 600. In an embodiment, a distancebetween said center of gravity and the longitudinal axis ‘A’ of thehammer 600 is less than approximately 20%, more preferably less thanapproximately 10%, of the full height of the hammer 600 as measured fromthe top of the handle 604 to the bottom of the battery pack 612.

In an embodiment, as discussed above, the first end cap 100 may bemounted over the main housing 602. The first end cap 100 may be securedto the main housing 602 by any known mean such as screws. Alternatively,as shown in FIG. 18, the first end cap 100 may be formed integrally aspart of the main housing 602 as a single piece.

In an embodiment, first end cap 100 may be provided with radial exhaustports as previously described in order to substantially isolate theairflow through the motor 500 from the main housing 602. In anembodiment, while some leakage of air from the first end cap 100 to themain housing 602 is possible, the air is substantially prevented fromentering the main housing 602. In this embodiment, an additional fan(not shown) may be provided on the motor shaft 340 above the crank wheel642 to cool the internal components of the hammer 600. Alternatively, asshown in FIG. 18, the first end caps 100 may be provided with a seriesof air vents 640 that allow flow of air from the motor 500 into the mainhousing 602 in a direction along the axis of the rotor shaft 340 forcooling of the internal components of the hammer 600.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will bethorough and will fully convey the scope to those who are skilled in theart. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

1. A brushless direct-current (BLDC) motor comprising: a stator having astator core, a plurality of teeth extending radially outwardly from thestator core, and a plurality of windings wound around the stator teeth;a rotor shaft extending along a center axis; a rotor having a rotor coredisposed around the stator, a plurality of permanent magnets secured tothe rotor core, an inner annular member mounted on the rotor shaft, anda plurality of radial blades extending angularly from the rotor core tothe inner annular member forming a fan adjacent the stator thatgenerates an airflow with rotation of the rotor shaft; a first end capincluding a radial back plate proximate the fan and a center opening inthe radial back plate through which the rotor shaft extends, the radialback plate including at least one sloped surface forming at least oneair gap, wherein the airflow generated by the fan is centrifugallyguided within the first end cap by the at least one sloped surface andcaused to exit the first end cap through the at least one air gap; and asecond end cap including a main body disposed adjacent the statoropposite the fan.
 2. The motor of claim 1, wherein the first end capfurther comprises an annular body formed at least partially around thefan, wherein the radial back plate extends from the annular body, theannular body including at least one exhaust port in fluid communicationwith the at least one air gap and through which the airflow is expelledfrom the first end cap in a substantially radial direction.
 3. The motorof claim 2, wherein the at least one sloped surface includes two slopedsurfaces disposed on two sides of the center opening of the first endcap, the at least one air gap includes two air gaps formed betweenrespective ends of the two sloped surfaces, and the two air gaps extendfrom the annular body of the first end cap towards the center opening tointersect a centrifugal path of the airflow within the first end cap. 4.The motor of claim 2, wherein the first end cap includes a side plateprojecting outwardly around the annular body and a lower surfacearranged to be mounted on a housing of a tool.
 5. The motor of claim 1,wherein the center opening of the end cap supports a front bearing ofthe rotor shaft.
 6. The motor of claim 1, wherein the second end capcomprises an annular body extending form the main body around at least aportion of the rotor core, the annular body of the second end cap cominginto contact and being secured to the first end cap.
 7. The motor ofclaim 1, wherein the second end cap comprises a first plurality ofopenings for passage of airflow and a second plurality of openings forpassage of a plurality of motor terminals arranged to electricallycouple to the plurality of windings of the stator.
 8. The motor of claim7, further comprising a stator collar mounted on the stator core,wherein the plurality of terminals is mounted on the stator collar in adirection parallel to the rotor shaft.
 9. The motor of claim 1, whereinthe second end cap comprises a center opening within which a sensorboard is secured, the sensor board accommodates a plurality ofpositional sensors facing the rotor shaft, and a sense magnet is mountedon the rotor shaft facing the plurality of positional sensors.
 10. Apower tool comprising: a housing; a battery receptacle formed on thehousing for receiving a power tool battery pack; a control moduledisposed within the housing to control supply of power from the batterypack; and a brushless direct-current (BLDC) motor mounted within or onthe housing, the motor comprising: a stator having a stator core, aplurality of teeth extending radially outwardly from the stator core,and a plurality of windings wound around the stator teeth; a rotor shaftextending along a center axis; a rotor having a rotor core disposedaround the stator, a plurality of permanent magnets secured to the rotorcore, an inner annular member mounted on the rotor shaft, and aplurality of radial blades extending angularly from the rotor core tothe inner annular member forming a fan adjacent the stator thatgenerates an airflow with rotation of the rotor shaft; a first end capmounted on the housing, the first end cap including a radial back plateproximate the fan and a center opening in the radial back plate throughwhich the rotor shaft extends, the radial back plate including at leastone sloped surface forming at least one air gap, wherein the airflowgenerated by the fan is centrifugally guided within the first end cap bythe at least one sloped surface and caused to exit the first end capthrough the at least one air gap; and a second end cap including a mainbody disposed adjacent the stator opposite the fan.
 11. The power toolof claim 10, wherein the first end cap further comprises an annular bodyformed at least partially around the fan, wherein the radial back plateextends from the annular body, the annular body including at least oneexhaust port in fluid communication with the at least one air gap andthrough which the airflow is expelled from the first end cap in asubstantially radial direction.
 12. The power tool of claim 10, whereinthe first end cap is integrally formed with the housing.
 13. The powertool of claim 10, wherein the power tool further comprises: a tubularcylinder housed within the housing defining a longitudinal axis; apiston reciprocatingly disposed within the tubular cylinder; a crankmechanism disposed within the housing configured to convert a rotarymotion to a reciprocating motion for driving the piston; a tool holdermounted on the housing forward of the tubular cylinder; and a batteryreceptacle provided on the housing for receiving a removable power toolbattery pack, the battery pack being provided on a first side of a planethat intersects the longitudinal axis when received within the batteryreceptacle, wherein the motor is mounted on the housing on a second sideof the plane that intersects the longitudinal axis such that a distancebetween the longitudinal axis and a center of gravity of the power toolwith the battery pack received within the battery receptacle is lessthan or equal to approximately 20% of a full height of the power tool.14. A lawn mower comprising: a main deck defining a lower cavity withinwhich a cutting blade is received; a plurality of wheels supporting themain deck; and a brushless direct-current (BLDC) motor mounted on themain deck for driving the cutting blade, the motor comprising: a statorhaving a stator core, a plurality of teeth extending radially outwardlyfrom the stator core, and a plurality of windings wound around thestator teeth; a rotor shaft extending along a center axis through anopening of the main deck to rotationally drive the cutting blade; arotor having a rotor core disposed around the stator, a plurality ofpermanent magnets secured to the rotor core, an inner annular membermounted on the rotor shaft, and a plurality of radial blades extendingangularly from the rotor core to the inner annular member forming a fanadjacent the stator that generates an airflow with rotation of the rotorshaft; a first end cap mounted on the main deck, the first end capincluding a radial back plate proximate the fan and a center opening inthe radial back plate through which the rotor shaft extends, the radialback plate including at least one sloped surface forming at least oneair gap, wherein the airflow generated by the fan is centrifugallyguided within the first end cap by the at least one sloped surface andcaused to exit the first end cap through the at least one air gap andabove the main deck; and a second end cap including a main body disposedadjacent the stator opposite the fan.
 15. The lawn mower of claim 14,wherein the first end cap further comprises an annular body formed atleast partially around the fan, wherein the radial back plate extendsfrom the annular body, the annular body including at least one exhaustport in fluid communication with the at least one air gap and throughwhich the airflow is expelled from the first end cap in a substantiallyradial direction.
 16. The lawn mower of claim 14, further comprising amotor housing disposed above the main deck to house the motor, and abattery cage disposed above the motor housing for receiving a removeablebattery pack therein.